The Collaborative International Dictionary of English v.0.48:

Nonperformance \Non`per*form"ance\, n.
   Neglect or failure to perform.
   [1913 Webster] nonphilosophic

WordNet (r) 3.0 (2006):

nonperformance
    n 1: failure to act with the prudence that a reasonable person
         would exercise under the same circumstances [syn:
         negligence, carelessness, neglect, nonperformance]

Moby Thesaurus II by Grady Ward, 1.0:

53 Moby Thesaurus words for "nonperformance":
   Sisyphean labor, culpa, culpable negligence, default, delinquency,
   dereliction, disconformity, disregard, endless task, failure,
   inadvertence, inadvertency, inattention, inexecution, inobservance,
   laches, laissez-faire, lapse, laxity, laxness, loose ends,
   looseness, neglect, neglectfulness, negligence, nonaccomplishment,
   nonachievement, nonadherence, noncompliance, nonconformance,
   nonconformity, nonconsummation, nondischarging, nonexecution,
   nonfeasance, nonfulfillment, noninterference, nonobservance,
   nonrestriction, omission, overlooking, oversight, permissiveness,
   poor stewardship, procrastination, remissness, rough edges,
   slackness, slight, unfulfillment, unobservance, unrigorousness,
   work of Penelope